In this lecture, I explore the significance of materiality and material religious approaches for understanding religious change and transmission during communism. Secret police archives as a body of sources, I argue, far from simply reflecting the ideological obsessions and repressive policies of communist regimes, offer an important entry point for understanding how religion was lived, transmitted and shaped during the period. The changes to the material basis, engagements and entanglements of religious life that we can trace through the secret police archives demonstrate the generative power of materiality in the production of religion.